Comment by defektunge

The easiest way to get these is to grow them yourself. Any level 85+ character who has done the Tillers introduction quests can produce 20 of these per day. A level 90 character who's gone through all the questing to unlock everything can produce 80 of these per day.

It's not the only way to get them, but five minutes of work for a guaranteed 20-80 turnips is going to be the easiest way.